Continuous rotary heating treating apparatus and method

ABSTRACT

Apparatus and method for continuously heat treating objects comprising a horizontally disposed cylinder, a charging means located at one end thereof and a discharge means at the other end thereof, with the inner surface of the cylinder having helical ribs forming grooves with heating means located within the cylinder, whereby rotation of the cylinder moves the objects from one end to the other while heat treating same.

Unlted States Patent [191 [111 Kawato Oct. 8, 1974 15 1 CONTINUOUS ROTARY HEATING 560,855 5/1896 om" 263/33 R TREATING A A S AND M H 1,173,188 2/1916 Hetherington 263/33 R 3,539,336 ll/l970 Urich 263/32 R [75] Inventor: Tomoyoshi Kawato, 8,12-chome,

Honcho Denencho fu, Ohta-ku, Tokyo, Japan [73] Assignee: Nippon Kokan Kabushiki Kaisha,

Tokyo, Japan [22] Filed: Dec. 28, 1971 21 Appl. No.: 213,106

[30] Foreign Application Priority Data Dec. 30, 1970 Japan 45-123,077

[52] US. Cl. 432/11 [51] Int. Cl F27b 7/14 [58] Field of Search 263/33, 32; 432/11, 105

[56] References Cited UNITED STATES PATENTS 440,468 11/1890 Clark ..263/33R Primary Examiner-John J. Camby Attorney, Agent, or Firm-Moonray Kojima charge means at the other end thereof, with the inner surface of the cylinder having helical ribs. forming grooves with heating means located within the cylin- Y der, whereby rotation of the cylinder moves the objects from one end to the other while heat treating same.

11 Claims, 4 Drawing Figures PATENTEDnm 8l974 3.840.333

sum 10F 3 'IIlIl/IIIIIIIII I m m PATENTEUUCI 81974 3.840.333

sumanr 3 I CONTINUOUS ROTARY HEATING TREATING APPARATUS AND METHOD BACKGROUND OF THE INVENTION This invention relates to rotary heat treating apparatus and method.

There are various types of heat treating apparatus in the prior art, such as those used for calcinizing or dry processing lime, cement and fertilizers, or for burning dust, dirt, garbage or for various other types of heat treatment. The apparatus may be either batch type or continuous feed type. Continuous heat treating is preferable from the point of efficiency and economy. The prior art continuous heat treating equipment for example a rotary kiln for calcining lime or cement, is arranged so that a cylindrical body is positioned oblique to the base. Because of this oblique position, the transfer of materials to the equipment is not uniform as to moisture content, specific gravity, or charging amounts. Thus, heat is not completely and thoroughly supplied to the material and heat treatment is irregular. High quality products are difficult to obtain. Moreover, conventional continuous heat treating apparatus are complex, entail high costs of maintenance, require expensive housing and pits for placement, and require special construction to keep the kilns at the oblique angle,etc.

The screw conveyor is used also for transfer of powder, grain or half solid materials. However, such a conveyor cannot be used for heat treatment as a rotary kiln because of such problems as passage of combustion gases and losses of materials on the conveyor.

SUMMARY OF INVENTION This invention has successfully eliminated the above defects and disadvantages of the prior art. Briefly, the

' invention comprises a horizontally disposed cylindrical body having a helically arranged rib on the inner surface thereof to-form a continuous groove extending from one end to another. Means for supplying heat are located at the center of the cylinder. Means are provided for rotating the cylinder. Products to be heated BRIEF DESCRIPTION OF DRAWING FIG. I is a cross sectional view of an illustrative embodiment of the invention;

FIG. 2 is a side view of FIG. 1 shown from the entry end;

FIG. 3 is a half sectional side view of FIG. 1 shown from the exit end; and

FIG. 4 is a partial sectional side view of another illustrative embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Turning now to FIGS. 1 to 3, cylindrical body 1 is supported by supporters (FIGS. 2, 3) spaced suitably on a base floor and provided on the outside thereof with a gear linkage 5, which is engaged with gear means 8, connected by belt to motor means 18. Body I is rotated about its axis by means of the gear and motor arrangment shown. The length and diameter of body I may be designed in accordance with the treatment desired. A charging device or port 3 is fixedly positioned at the right or entry end 12 of body 1 as shown, by plate 4 and collar 16. It does not rotate with body 1.

At the' left or exit end is positioned adischarge port or device 6 having a flange 2l attached to body I between holding means 7 and end member 13. The discharge port 6 is fixed at its lower portion with suitable means (not shown) to keep it free from rotation of body 1. It discharges a selected amount of treated products during each revolution of the body. It is also possible to design the lower portion to rotate with body I and thus discharge selected amounts of products periodically. I

The internal mechanism of body 1 comprises helical ribs 25 on the inner surface thereof forming grooves 2 which extend from one end thereof to another end. The ribs are of suitable height and pitch. Within each groove is a projection 22 which'assists the turning of objects placed in the cylinder for heat treatment. A fuel pipe 14 is located in the center or axis of the cylinder. For example, the heating element maybe a gas pipe line connected to a gas supply (not shown) with nozzles or burners l5, whicharefired to produce open flame heating. Pipe 14 is held fixedly at end 24 by a cap 23 at the entry end of the cylinder,'in such a manner that the cylinder will rotate about it. The entire cylinder is substantially sealed so that heat will'not escape and the products to be heated willnot be released or exposed to the environment. Other types of heaters can be used. For example, the fuel pipe may have a nozzle thereon which is placed within the discharge end of the cylinder and fuel caused to jet out of the nozzle. Heating can be done by means located outside of the body or underneath the body.

The operation of the foregoing embodiment will be explained after describing the embodimentof FIG. 4,

in which cylinder 1 is supported by supporters 10 on' pillars or bases which are spaced suitably on base floor 20. Body 1 is rotated by means of a linkage 5, driver or motor 18, gear box 18' and gears 8. Continuous helical grooves'2 are formed on the inner surface of body 1 by continuous helical ribs 25. Within each groove 2 is fixed a projection 22, in the same manner as FIG. 1.

A preheater 27 isdisposed in front or entry end 12 (in this embodiment on the left. end) of body '1. The preheater 27 is mounted by means of a metal connector 28 and air sea] means 29 located between the entry end 12 and metal connector 28 to prevent leakage of com bustion gases or discharge gases. There is a transfer means 30 within preheater 27 to move forward preheated materialsTransfer means 30 is equipped with a chute 31 whose end 3 is fit into the opening of body 1, thereby maintaining the transfer means at a predetermined position. At the other end (delivery or exit end located to the right in this embodiment) a hood means 32 is mounted on body 1 as shown. Air sealing means 33 are provided on the outside of this mounted portion. A fuel pipe 14 is inserted into this hood 32 at the center of body 1 with a nozzle 15at its tip inserted within the body. A cooler means 35 is provided under hood means 32 and below discharge port 6, so that heat treated products may be released therein after discharge through discharge port 6.

The operation of the two embodiments will now be explained.

Cylindrical body 1 is rotated at a constant speed by motor 18 turning gears in gear box 8, which turns gear teeth 9 of linkage 5. Concurrently, fuel is fed into pipes 14 and is burned at burners or nozzles 15. During this time, materials to be heat treated are selectively charged into helical grooves 2 of cylinder 1 via charging device 3 (and through chutes and transfer means 30 and 31 in FIG. 4). A constant amount of of materials are moved forward (to left in FIG. 1, to right in FIG. 4) to the discharge port 6, due to the helical movement of ribs and grooves 2 which are of suitable constant pitch, and are concurrently heat treated. When body 1 is rotated, the treated materials will be moved foward helically as they come together at the bottom of grooves 2 due to the weight of the materials. During the forward movement, a desired amount of heat is applied to carry out the heat treatment, such as calcination, burning or drying, etc.

The projections 9 fixed to the bottoms of grooves 2, turn the materials as the body rotates. Thus, the turning action exposes the materials evenly and uniformly to the heat. Heat treatment is even and uniform. Gases generated by the heating are discharged out of the charging port and removed from an exhaust port (not shown).

In the embodiment of FIG. 4, the waste heat is used to preheat by transfering-the heat from cylinder 1 to the preheater 27 by passage way (not shown). The material tobe heat-treated is thus preheated by the waste heat. After preheating the materials are" charged into the body 1 through charging port '3 from chute 31. After the main heatin'g, the productsare discharged out of port 6.in av constant amount, and subsequently are cooled in cooler means 35. Thereafter the heat treated products may be removed-for further treatment, such as grinding, filtering, and the like.

Actual experiments were performed according tothe invention. The results are as follows:

EXAMPLE 1 i A cylindrical body of 60 meter length and 2.9 meter inner diameter and provided with a preheater at the entry end thereof and with a product cooler at the exit end thereof, was charged with 0.4 tons'of limestone (CaCO.-;) per one rotation (i.e., 0.4 tons of limestone per pitch of the helical grooves). The burners at the discharging end was controlled so that the temperature at the exit end was 1,300C and at the entry end was l,l( )OC. The cylindrical body was rotated at 1.2 r.p.m. by means of the motor means, gear reduction box, and gears. After 78 rotations (i.e. after 65 minutes after charging) burnt lime (CaO) of high quality was discharged at the rate of 0.23 tons per revolution.

Compared to the conventional rotary kiln having oblique position, the calcination time was shortened about 30 minutes and the quality of the resultantprod- CaO, but those in the center of the limestone are still CaCO Toovercome this effect, in the prior art, the burnt limestone is further burnt until the whole structure is CaO, and only after that is the product removed.

EXAMPLE 2 (Production of portland cement) lathe cylindrical kiln of this invention. A cylfidric al body 62 meters length and 3.16 meter inner diameter,

- and having helical grooves of 1.3 meters pitch, was

uct was uniform and yield was high. Such differences is believed to be attributable to the following reasons.

The bunrt lime is generally given the chemical expression CaCO Ca0 CO 42.9 Kcal. Since the limestones are not sufficiently turned by the rotary kiln, the surface layer of limestone is burnt, and becomes charged with 1.1 tons of limestone, together with 0.4 tons of clay, and 0.3 tons of slag. The body was rotated at the speed of 1.3 rpm. The temperature was controlled so that the exit temperature was l,350C and that at the entry end was at 1,100C. After 48 rotations (i.e., after sixty minutes from time of charging) portland cement of high quality was discharged at the rate of 1.1 tons for each rotation.

Comparedwith the conventional kilns having oblique positions the calcination time was shortened about 20 minutes and the quality of the products was uniform and the yield was high. I

According to this invention, charged materials fed into helical grooves 2 are moved forward in order and at a certain amount and at a constant speed, due to the helical movement of the ribs and are well turned byprojections 22 disposed between the ribs 25 and in grooves 2, thereby uniformly and thoroughly supplying heat treatment to the charged materials so that prod ucts of high quality are obtained or perfect combustion is obtained. Furthermore, cylindrical body 1 is arranged in paralle. with base 20, i.e., horizontally, and therefore the height of the housing islowered and the costs of construction and maintenance are substantially reduces.

The foregoing is intended to be only illustrative of the principles of the invention. Numerous modifications and variations thereof would be apparent to one skilled in the art. All such modifications and variations are to be considered to, be within the spirit and scope of the invention.

What is claimed is:

1. A continuous rotary heat treating apparatus comprising a horizontally disposed cylindrical body means having an entry end and an exit end; motor means for rotating said body; charging means located at said entry end for charging items to be heat treated into said body; discharge means located at said exit end for discharging heat treated items; heating means for supplying heat to the inside of said body; and means for constantly moving predetermined amounts of said items from said entry end to said exit end while said body is being rotated by said motor means and while said heating means supplies heat to said body, said. heating means comprising a plurality of sources located longitudinally along substantially the axis of said cylindrical body.

height, said rib being on the inner surface of said body.

3. Apparatus of claim 2, wherein said means for constantly comprises turning means disposed in said groove.

4. Apparatus of claim 3, wherein said turning means comprises projections fixed to the inside of said body between said ribs.

5. Apparatus of claim 4, wherein said projections are located perpendicular to said helical grooves and are arranged cetripetally.

6. Apparatus of claim 1, wherein said charging means and said discharge means are disposed at predetermined positions and free from rotation of said body.

7. Apparatus of claim 1, wherein said heating means comprises burners positioned at substantially the axis of said body.

8. Apparatus of claim 7, wherein said heating means comprises a fuel pipe means extending through said body and fixed to a cap on said entry end.

9. Apparatus of claim 1, wherein a preheater is disposed at said entry end and cooler means is disposed at said exit end, said preheater being connected to receive waste heat from said cylindrical body.

10. Method of heat treating items in a continuous manner comprising the steps of charging said items into a cylinder having a horizontally disposed rib defining helical grooves on the inner surface of said cylinder;rotating said cylinder to move said items from one end thereof to another end thereof through helical movement of said ribs; heating the inside of said cylinder with a plurality of sources located longitudinally at substantially the axis of said cylinder; turning said items during said rotation of said cylinder thereby to expose said items so as to evenly apply said heat thereto; and discharging said items after heat treatment.

11. Method of claim 10, further comprising the step of preheating said items prior to charging into said cylinder; said preheating being by heat exhausted from said cylinder. 

1. A continuous rotary heat treating apparatus comprising a horizontally disposed cylindrical body means having an entry end and an exit end; motor means for rotating said body; charging means located at said entry end for charging items to be heat treated into said body; discharge means located at said exit end for discharging heat treated items; heating means for supplying heat to the inside of said body; and means for constantly moving predetermined amounts of said items from said entry end to said exit end while said body is being rotated by said motor means and while said heating means supplies heat to said body, said heating means comprising a plurality of sources located longitudinally along substantially the axis of said cylindrical body.
 2. Apparatus of claim 1, wherein said means for constantly comprises a helically disposed groove of desired depth formed by helically disposed rib of desired height, said rib being on the inner surface of said body.
 3. Apparatus of claim 2, wherein said means for constantly comprises turning means disposed in said groove.
 4. Apparatus of claim 3, wherein said turning means comprises projections fixed to the inside of said body between said ribs.
 5. Apparatus of claim 4, wherein said projections are located perpendicular to said helical grooves and are arranged cetripetally.
 6. Apparatus of claim 1, wherein said charging means and said discharge means are disposed at predetermined positions and free from rotation of said body.
 7. Apparatus of claim 1, wherein said heating means comprises burners positioned at substantially the axis of said body.
 8. Apparatus of claim 7, wherein said heating means comprises a fuel pipe means extending through said body and fixed to a cap on said entry end.
 9. Apparatus of claim 1, wherein a preheater is disposed at said entry end and cooler means is disposed at said exit end, said preheater being connected to receive waste heat from said cylindrical body.
 10. Method of heat treating items in a continuous manner comprising the steps of charging said items into a cylinder having a horizontally disposed rib defining helical grooves on the inner surface of said cylinder; rotating said cylinder to move said items from one end thereof to another end thereof through helical movement of said ribs; heating the inside of said cylinder with a plurality of sources located longitudinally at substantially the axis of said cylinder; turning said items during said rotation of said cylinder thereby to expose said items so as to evenly apply said heat thereto; and discharging said items after heat treatment.
 11. Method of claim 10, further comprising the step of preheating said items prior to charging into said cylinder; said preheating beiNg by heat exhausted from said cylinder. 